DE69216861T2 - WARM-CURING COATING COMPOSITIONS - Google Patents

Abstract

Disclosed are certain novel 2,2'-bisacetoacetates useful as crosslinking agents and a process for the preparation therefor. Also provided are novel enamel compositions containing the crosslinkers and coatings and articles coated with thermosetting coating compositions crosslinked with these novel crosslinkers.

Description

This invention relates to the field of organic chemistry. In particular, it relates to certain 2,2'-bisacetoacetates useful as polymer crosslinking agents in thermosetting coating compositions.

Background of the invention

Polymer crosslinking agents or "crosslinkers" are multifunctional molecules that can react with pendant functional groups on the polymers. The use of crosslinkers makes it possible to increase the molecular weight of polymers, usually in one step, and thus improve the properties of the resulting polymer or polymer film. Most crosslinking reactions are initiated by heating a mixture of the polymer and the crosslinker either as such or in a solvent. Such systems are often referred to as "thermosetting" systems.

Crosslinkers are particularly useful in coating applications because the crosslinker enables the use of relatively low molecular weight polymers and resins that are easily handled in solvents. The formulation can then be applied to a substrate and heated or cured to produce the final (heat cured) coating. This allows one to take advantage of the ease of handling and solubility properties of the low molecular weight plastics used in the formulations and then develop the hardness, chemical and solvent resistance, and strength/flexibility properties desired in the finished coating via the reaction of the crosslinker with the plastic during the curing process.

Crosslinkers are becoming increasingly important as more environmentally friendly coatings are becoming more important. A major environmental problem in the coatings industry is the amount of organic solvents released during the curing process. This solvent concentration or Volatile Organic Content (VOC) is a problem because of the role of organic solvents in the development of photochemical smog. For these reasons, many Governments, including the United States government, are reducing VOC concentrations in coating formulations. One way to reduce the amount of solvent required in a coating formulation is to reduce the molecular weight of the plastic backbone used in the formulation. However, following this approach makes cross-linking even more critical to developing the final properties of the cured film. Consequently, in these applications, the cross-linker enables a more sensible, environmentally friendly coating formulation.

Properties of cross-linked films and coatings:

A large number of properties are desirable in a coating to achieve the desired protection of the object against corrosion and other environmental factors. Some protective properties that are desirable to achieve are the resistance of the coating to various chemicals and solvents, the impact resistance of the system, the hardness of the coating and the weather resistance or the resistance of the system to various factors related to environmental influences.

1) Chemical and solvent resistance

In order to provide a coating with the required protection for the coated object, it must be resistant to various chemicals and solvents. If a coating is not resistant to solvents and chemicals, the coating could be removed or the protective layer could be compromised by common exposures such as cleaning agents or gasoline. Since the coating formulation is usually used in a solvent, the development of solvent resistance in the coated film indicates a change in the chemical nature of the coating formulation. This change is related to the cross-linking of the polymer. A common test to examine this property is the methyl ethyl ketone (MEK) rub resistance of the coating. The MEK rub resistance of a coating is often the best method of determining the extent of cross-linking in the coatings. For most applications, a MEK rub resistance of greater than 175-200 is generally desirable.

II) Impact resistance

In order for a coating to be resistant to collisions and other sudden impacts, the material must have certain strength properties.

If a coating does not have sufficient strength to withstand impacts and/or collisions, the coating will crack and break, compromising the protective integrity of the film. A test commonly used to determine the impact strength of a coating (ASTM D2794-84) is to drop a weight from various heights onto a panel and determine the force (in foot-lbs.) required to break the coating. Proper cross-linking helps develop the impact strength of a coating.

III) Hardness

In order for a coating to be resistant to scratching and other abrasions, the coating must have a certain degree of hardness. This resistance to scratching is often determined by scratching the coating with pencils of different hardnesses and recording the pencil hardness that actually scratches the coating.

Hardness and impact resistance often develop in opposite directions. This is due to the fact that impact resistance represents both the strength and flexibility of the polymer film, whereas hardness essentially represents the strength or rigidity of the film. Consequently, a combination of hardness and flexibility is often sought, compensating for one of the above properties by the other.

The compensation of these two factors is best understood by turning to the theory of crosslink density. If the coating formulation consists of a group of polyfunctional (n>2) polymer molecules and crosslinkers, the crosslinking process can be thought of as a series of steps. Initially, the crosslinking reaction consists of intermolecular reactions of different polymer chains. During the initial phase, the polymer and crosslinker chains combine and thus molecular weight builds up. However, the mobility of the resulting polymer chains is not greatly hindered. This stage could be characterized as improving the chemical resistance, hardness and impact strength of the film. At a certain point, however, the intramolecular reaction is essentially complete and intramolecular reactions become significant. At this point, the polymer becomes stiffer because polymer chain mobility is hindered by the intramolecular reactions and, consequently, more brittle coatings are obtained. At this stage, the hardness will improve, but the impact resistance will decrease due to the increased stiffness of the polymer network. The balance between flexibility and hardness can be controlled by the amount of crosslinker used, the average functionality of polymer and crosslinker, and the chemical structure of polymer or crosslinker.

IV) Resistance to atmospheric stress (ventilation)

Since many coated objects are exposed to severe weather conditions, the coating performance under various stressful conditions is very important. Factors that affect the weather resistance of a coating include the composition of polymer and crosslinker and the degree of crosslinking. A variety of stress tests are available that make it possible to determine the performance of the system under stressful conditions.

Crosslinkers currently used in this technical field:

A variety of cross-linkers are used in different areas of application. A non-exhaustive list of the functional groups commonly used in cross-linkers includes:

Epoxy compounds

Isocyanates

Aminoplastics

Unsaturated compounds

These materials advantageously utilize the reaction of the above-mentioned functional groups with various pendant groups of the polymeric backbones. These cross-linkers can be used in combination with other cross-linkers to impart a variety of desired properties to the coatings. The use and reactions of these cross-linkers have been discussed elsewhere (see, for example, Labana, S.S., in "Encyclopedia of Polymer Science and Engineering," Vol. 4, pp. 350-395). All of these materials are structurally very different from the 2,2'-bis-C1-C6 alkyl acetoacetates used in the present invention described below.

The present invention provides various novel 2,2'-bisacetoacetates that can be used as crosslinking agents in thermosetting coating compositions and a process for preparing the same. In addition, novel curable gloss coating compositions are provided comprising the above-mentioned novel 2,2'-bisacetoacetate crosslinking agents.

The present invention provides compounds of formula (1):

wherein R is a C₄-C₁₀ tertiary alkyl radical, R¹ is C₁-C₆ alkyl or aryl, and A is a group of the formulas

wherein R² is phenyl or A is a C₁-C₁₀ hydrocarbon radical, excluding compounds wherein both R's are tertiary butyl, both R¹'s are methyl and A is a methylene, ethylene or

group is.

Cornforth, et al., in the Journal of Chemical Society, Vol. 1959 No. 3, August 1959, pp. 2539-2547, describe the stereoselective synthesis of squalene. In particular, they disclose t-butyldiacetyl adipate and its chlorinated derivative. These two compounds are not claimed in the present invention. A study by G. Näslung, et al. in Acta Chemica Scandinavica, Vol. 16, No. II, 1962, pp. 1329-1336, relates to a new process for the preparation of 1-methylcyclohexan-1-one-3 and derivatives thereof. Furthermore, this study discloses the preparation of certain t-butyldiacetylmalonates in which the bridging -CH-₂- group (corresponding to -A- of formula (1) above) is substituted with a methyl, n-propyl, phenyl or 2-furyl residue. These compounds are also not claimed.

Compounds of formula (1) above are useful as crosslinking agents in thermosetting coating compositions as described in more detail below.

Furthermore, it is well documented that compounds such as those above, in which

are difficult to isolate because subsequent cyclization leads to cyclohexyl compounds of formula (2):

According to a further aspect of the present invention there is provided a process for preparing compounds of formula (I)

wherein A is a group of the formula -CH₂- and R¹ is C₁-C₆ alkyl or aryl, comprising contacting a mixture of the C₄-C₆ tertiary alkyl beta-keto ester of the formula

and aqueous formaldehyde with a basic ion exchange resin.

In the above process, it is preferred that the aqueous formaldehyde solution contains about 20 to 35% formaldehyde relative to water.

The basic ion exchange resin used in the present invention may be a strong basic ion exchange resin. These materials are typically obtained from either styrene/divinylbenzene polymers or acrylic/divinylbenzene polymers and contain a quaternary amine/hydroxide complex. Examples of such resins are Amberlite IRA-400, 402/440, 938, 900 and IRA 458 from Rohm and Haas, Duolite A-109, A-161 and A-132 also from Rohm and Haas and Dowex SBR-P, SBR and MSA-1 from Dow Chemical.

It is further preferred that the process is carried out at a temperature of 18°C to 40°C, with 25-35°C being particularly preferred.

According to a further aspect of the present invention, there is provided a curable gloss coating composition comprising

(a) 95 to 55% by weight, based on the total weight of (a) and (b), of one or more curable polymers,

(b) 5 to 45% by weight, based on the total weight of (a) and (b), of a compound of formula (1)

wherein R is a C -C tertiary alkyl radical, R¹ is C₁-C₆ alkyl or aryl and A is a group having the formulas

wherein R² is phenyl or A is a C₁-C₁₀-hydrocarbon radical, and

(c) 0 to 50% by weight, based on the total weight of (a) and (b), of a solvent.

In the curable gloss coating composition described here, the weight percentages are based on the total weight of (a) and (b), i.e. the binder. Thus, if the weight of (a) and (b) in a given composition is 100 g, the total weight of component (c) is up to 50 g (similarly for component (d) as indicated below).

It is further preferred that component (a) be present in a range of 85 to 60 wt.%, that component (b) be present in a range of 15 to 40 wt.%, and that component (c) be present in a range of 0 to 35 wt.%. Component (a) may be any curable polymer having free hydroxy groups. Examples of such polymers are polyesters and acrylic type polymers.

The curable polyester component (a) can be obtained by condensation polymerization processes known per se. The most preferred method is to melt all the reactants in a reactor of suitable size, heat the reactants to initiate the reaction and continue processing until the desired molecular weight is obtained. A reaction is evidenced by the accumulation of water (direct condensation) or alcohol (ester interchange). This process is called a fusion process and can be carried out at atmospheric pressure or vacuum. No modifications to this standard process are required to prepare suitable polymers for component (a), above.

In such curable polyesters, the diol and/or polyol residues are selected, preferably from the following residues: ethylene glycol, propylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2,2-dimethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, thiodiethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, p-xylylenediol, diethylene glycol, triethylene glycol, tetraethylene glycol and pentaethylene, hexaethylene, heptaethylene, octaethylene, nonaethylene and decaethylene glycols.

Furthermore, the carboxylic acid residue of the curable polyester is preferably selected from the following acids: oxalic acid, malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid, 2,5-norbornanedicarboxylic acid, 1,4-naphthanlic acid, diphenic acid, 4,4,-oxydibenzoic acid, diglycolic acid, thiodipropionic acid, 4,4,-sulfonyldibenzoic acid and 2,6-naphthalenedicarboxylic acid.

Examples of commercially available curable polyesters (component (a)) include Cargill 5770, Cargill 5722 and Aroplaz 6455 (Spencer Kellogg).

In general, these polyesters have a hydroxyl value of about 20 to 200 (mg KOH/g polymer).

The acrylic polymer component (a) is preferably a polymer or plastic, prepared by polymerizing hydroxyl group-bearing monomers such as: hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxyhexyl acrylate, hydroxyhexyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate and the like, optionally polymerized with other monomers such as: methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, styrene, vinyl acetate and the like. The ratio of the reagents and the molecular weights of the acrylic polymers obtained are preferably selected so as to obtain polymers with an average functionality (number of OH groups per molecule) greater than or equal to 2, preferably greater than or equal to 4.

Examples of commercially available curable acrylic polymers include Joncryl 800, Joncryl 500, and Neocryl LE-800.

Suitable solvents for curable gloss coating compositions (component (c)) include ketones (e.g. methyl amyl ketone), glycol ethers, e.g. 2-butoxyethanol, glycol ether esters, e.g. ethyl 3-ethoxypropionate (EEP) and methoxypropyl acetate, toluene, ester solvents such as ethyl acetate, butyl acetate and propyl acetate, alcohols such as butanol, 1-methyl-2-pyrrolidinone, xylenes and other volatile inert solvents typically used in baking (i.e. heat curing) gloss coating compositions.

The term C₁-C₁₀ hydrocarbon radical preferably means a divalent alkylene group. Examples of such groups are methylene, ethylene and propylene.

The term "aryl" refers to heterocyclic aryl rings and carbocyclic aryl rings. For example, aryl can be phenyl, naphthyl, phenanthryl. Aryl can also be a 5 to 6 membered heterocyclic ring which can contain one oxygen atom and/or one sulfur atom and up to three nitrogen atoms, with the heterocyclic aryl ring optionally fused to one or two phenyl rings. Examples of such ring systems include: thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, Isoxazolyl, triazolyl, thiadiazolyl, oxadiazolyl, tetrazolyl, thiatriazolyl, oxatriazolyl, pyridyl, pyrimidyl, pyrazinyl, pyridazinyl, thiazinyl, oxazinyl, triazinyl, thiadiazinyl, oxadiazinyl, dithiazinyl, dioxazinyl, oxathiazinyl, tetrazinyl, thiatriazinyl, oxatriazinyl, dithiadiazinyl, imidazolinyl, dihydropyrimidyl, tetrahydropyrimidyl, tetrazolo, pyridazinyl and purinyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl.

According to a further aspect of the present invention there is provided a curable gloss coating composition further comprising one or more crosslinking catalysts, for example dibutyltin laurate, stearic acid, butylstannoic acid, dibutyltin oxide, zinc acetylacetonate and 1,3-diacetoxy-1,1,3,3-tetrabutyldistannoxane.

According to a further aspect of the present invention there is provided a crosslinkable gloss coating composition as described above, further comprising one or more leveling agents, flow agents or flow control agents, sanding agents, pigment wetting and dispersing agents and surfactants, ultraviolet absorbers, ultraviolet light stabilizers, coloring dyes, defoaming and anti-foaming agents, anti-seat and anti- bow agents and body-forming agents, anti-skinning agents, anti- overflow and anti-flow agents, fungicides and anti-mold agents, corrosion inhibitors, thickeners or coalescing agents.

Specific examples of such additives can be found in "Raw Materials Index, published by the National Paint & Coatings Association, 1500 Rhode Island Avenue, N.W., Washington, D.C., 20005.

Examples of smoothing agents include synthetic silica available from Davison Chemical Division of W.R. Grace & Company under the trade name Syloid, polypropylene available from Hercules Inc. under the trademark Hercoflat, synthetic silicate available from J.M. Huber Corporation under the trade name Zeolex Examples of dispersants and surfactants include: sodium bis(tridecyl)sulfosuccinate, di(2-ethylhexyl)sodium sulfosuccinate, sodium dihexylsulfosuccinate, sodium dicyclohexylsulfosuccinate, diamylsodium sulfosuccinate, sodium diisobutylsulfosuccinate, disodium iso-decyl sulfosuccinate, disodium ethoxylated alcohol half ester of sulfosuccinic acid, disodium alkylamido polyethoxysulfosuccinate, tetrasodium N-1,2-dicarboxyethyl)N-oxtadecyl sulfosuccinamate, disodium N-octasulfosuccinamate, sulfated-ethoxylated nonylphenol, 2-amino-2-methyl-1-propanol.

Examples of viscosity, dispersion and flow control agents include polyaminoamide phosphate, carboxylic acid salts of high molecular weight polyamine amides and alkylene amine salts of unsaturated fatty acids, all available from BYK Chemie U.S.A. under the trade name Anti Terra. Other examples are polysiloxane copolymers, polyacrylate solution, cellulose esters, hydroxyethyl cellulose, hydrophobically modified hydroxyethyl cellulose, hydroxypropyl cellulose, polyamide wax, polyolefin wax, carboxymethyl cellulose, ammonium polyacrylate, sodium polyacrylate and polyethylene oxide.

Some proprietary antifoam agents are commercially available, for example, under the trade name Brubreak from Buckman Laboratories Inc., under the trade name Byk from BYK Chemie, U.S.A., under the trade names Foamaster and Nopco from Henkel Corp. /Coating Chemicals, under the trade name Drewplus from Drew Industrial Division of Ashland Chemical Company, under the trade names Troysol and Troykyd from Troy Chemical Corporation, and under the trade name SAG from Union Carbide Corporation.

Examples of fungicides, anti-mold agents and biocides are 4,4-dimethyloxazolidine, 3,4,4-trimethyloxazolidine, modified barium metaborate, potassium N- hydroxy-methyl-N-methyldithiocarbamate, 2-(thiocyanomethylthio)benzothiazole, potassium dimethyldithiocarbamate, adamantane, N-(trichloromethylthio)phthalimide, 2,4,5,6-tetrachloroisophthalonitrile, orthophenylphenol, 2,4,5-trichlorophenol, dehydroacetic acid, copper naphthenate, copper octoate, organic arsenic, tributyltin oxide, zinc naphthenate and copper 8-quinolinate

Examples of U.V. absorbers and U.V. light stabilizers include: substituted benzophenone, substituted benzotriazoles, hindered amines and hindered benzoates available from American Cyanamide Company under the trade designation Cyasorb UV and diethyl 3-acetyl-4-hydroxy-benzyl phosphonate, 4-dodecycloxy-2-hydroxybenzophenone and resorcinol monobenzoate.

Such paint or coating additives described above form a relatively small proportion of the gloss coating compositions, preferably 0.05 wt.% to 5.00 wt.%.

According to a further aspect of the present invention there is provided a curable gloss coating composition optionally containing one or more of the additives described above.

According to another aspect of the invention, there is provided a gloss coating composition further comprising one or more other crosslinking agents. Typical crosslinking agents useful in this context include various melamine-type crosslinking agents, i.e., crosslinking agents having a plurality of N-CH₂OR groups with R=C₁-C₈ alkyl. Preferred melamine-type crosslinking agents in this regard include: hexamethoxymethylolmelamine, hexabutoxymethylolmelamine, and various hexaalkoxymethylolmelamines where the alkoxy group may be C₁-C₈ alkyl, and mixtures thereof. Also included are: tetramethoxymethylolbenzoguanamine, tetramethoxymethololurea, and corresponding hexaalkoxymethylol derivatives.

Other crosslinking agents that can be used with the compounds of the present invention include: various aliphatic and aromatic polyisocyanates, for example, isophorone diisocyanate, tetramethylxylylene diisocyanate, hexamethylene diisocyanate, methylene bis (4,4'-cyclohexyl isocyanate), toluene diisocyanate, methylene bis (4,4'-phenyl isocyanate), and the like. The above-mentioned isocyanates can be used in either blocked or unblocked form and they can be derivatized in a variety of ways. These derivatized isocyanates include isocyanurates, biurets, allophanates, and uritidinediones. (See, for example, J. K. Backus in "High Polymers", Vol. 29, 1977, pp. 642-680).

According to a further aspect of the present invention, there is provided a curable gloss coating composition as specified above, which further contains one or more pigments in a concentration of about 1 to about 70 wt.%, preferably about 30 to about 60 wt.%, based on the total weight of components (a) and (b) of the composition.

Pigments suitable for use in the gloss coating compositions of the present invention are typically organic and inorganic pigments well known to one skilled in the art of surface coatings, particularly those listed in the Colour Index, Colour Index, 3rd Edition, 2nd Revision, 1982, published by the Society of Dyers and Colourists in association with American Association of Textile Chemiste and Colorists. Examples include: CI Pigment White 6 (titanium dioxide), CI Pigment Red 101 (red iron oxide), CI Pigment Yellow 42, CI Pigment Blue 15, 15:1, 15:2, 15:3, 15:4 (copper phthalocyanines), CI Pigment Red 49:1 and CI Pigment Red 57:1.

In the formulation of the above-mentioned curable gloss coating compositions, the desired substrate or article is then coated, ie, the steel, aluminum or galvanized surface (either pretreated or unpretreated) which is then heated (ie cured) at a temperature of 140°C to 275°C for a period of 1-120 minutes and thereafter allowed to cool. According to a further aspect of the present invention there is provided a shaped or molded article which has been coated with a thermosetting coating composition according to the present invention and then cured.

Further examples of typical applications and curing processes can be found in US-A-4,737,551 and US-A-4,698,391.

According to another aspect of the present invention, there is provided a coating resulting from applying and curing the curable gloss coating composition as set forth above.

Experimental part

1H and 13C NMR spectra were obtained on a Varian model Gemini 300 in CDCl3 at frequencies of 300 and 75 MHz, respectively. Carbon multiplicities, where indicated, were determined using a DEPT pulse sequence. (See, for example, Doddrell, D. M.; Pegg, D. T.; Bendall, M. R.; J. Magn. Reson. 48, 323, (1982)). Mass spectra were obtained on a VG ZAB or 7070VSEQ. High-resolution CI mass spectra (HR-CIMS) were obtained by the method of Haddon et al., Proceedings of 36th ASMS Conf. June 5-8, (1988), 1396.

The test procedures used were the following:

1. Examination of coated metal samples at 100% relative humidity - Cleveland Humidity Test (ASTM method D 2247)

2. Ford Cup Viscosity (ASTM Method D 1200)

3. Film thickness (General Electric Gage, Type B)

4. Film hardness (pencil method, ASTM 3363-74, reaffirmed 1980)

5. Solvent resistance (dynamic abrasion test with methyl ethyl ketone (MEK), ASTM method D 1308)

6. Impact strength (ASTM method D 2794-84)

7. Molecular weight of plastic-GPC

8. OH value determined by titration and given in units of mg KOH consumed per gram of polymer

9. Acid number (ASTM method D 465). The units of this value are the same as for the OH value.

The following plastics were used in the evaluations.

PLASTIC A:

This material is an acrylic resin made from 20 mol% hydroxyethyl methacrylate and 80 mol% methyl methacrylate and had a hydroxyl value of 106. The plastic was used in a solution of 60% solids in ethyl 3-ethoxypropionate (EEP).

PLASTIC B:

This material was a polyester prepared in a two-step addition process from 16.1 moles of neopentyl glycol, 5.0 moles of trimethylolpropane, 11.8 moles of cyclohexanedicarboxylic acid, and 8.9 moles of phthalic anhydride. The material had a Mw=16000, a Mn=2400, a hydroxyl value of 94, and an acid value of 9. This material was diluted with xylene to a solution containing 65-75% solids.

PLASTIC C:

This material was prepared from 12.60 moles of terephthalic acid, 0.66 moles of 1,4-cyclohexanedicarboxylic acid and 15.20 moles of 1,6-hexanediol. The resulting material had a hydroxyl number of 42.5 and an acid number of 2.3, an Mn of 3666 and an Mw of 9027

PLASTIC D:

This material was an amorphous polyester containing terephthalic acid, neopentyl glycol and 9-10% (relative to neopentyl glycol) trimethylolpropane. It had a hydroxyl number of 65, an acid number < 10, a Mn of about 3000 and a Mw of about 10,000.

PLASTIC E:

This material was prepared in a two-step condensation from 3.12 mol NPG, 1.38 mol TMP, 1.47 mol dimethylcyclohexanedicarboxylate and 2.21 mol Isophthalic acid. The resulting plastic had an OH value of 152 and an acid number of 2.1.

Example 1 - Preparation of 2.4-diacetyl-di-t-butylglutarate (la)

In a 1 L 3-neck flask equipped with a mechanical stirrer, nitrogen inlet and thermometer were placed 500.04 g (3.161 mol) of t-butylacetoacetate (tBAA) and 158.16 g of aqueous formaldehyde (30% formaldehyde, 1.582 mol). The flask was placed in an ice-water bath and 10.3 g of Amberlite R IRA 400 (OH) catalyst was added. The solution exothermed to about 35°C upon addition of the catalyst. The reaction mixture was stirred at room temperature for 4 days after which the catalyst was recovered by filtration and the organic phase was separated from the aqueous layer. The crude organic material was purified by wiped film distillation at 130-140°C/0.2 mm Hg. An analytical sample was obtained by recrystallizing the distilled material from MeOH/H2& and washing the resulting crystals with cold heptane, mp 46.5-49.5°C.

¹H-NMR (CDCl₃) 1.43 (s, 18 H), 2.18-2.23 (m,-2H), 2.20 (s, 6H), 3.38 (t, J=7, 33Hz, 2H). 13C-NMR 25.25 (CH2), 27.58 (CH3), 28.69 (CH3), 57.62 (CH), 82.26 (C), 168.38 (C), 202, 94 (C). IR: 2890-2860, 1730, 1710, 1150 cm¹, analytically found C: 62.30%, H: 8.93% (calculated for C₁₇H₂₈O₆C 62.16%, H 8, 61%). HR-CIMS 346.2213 (calculated for C₁₇H₂₈O₆+NH₄: 346.2221).

Example 2 - Preparation of 2.4-diacetyl-di-(ethyl)-glutarate (1c)

This material was prepared as above by stirring 500 g (3.84 mol) of ethyl acetoacetate (EAA), 189 g of 37% aqueous formaldehyde (2.33 mol), and 10.3 g of Amberlyst IR 400 (OH) for 3 days. The resulting homogeneous solution was extracted with saturated NaCl/CH2Cl2, concentrated in vacuo, and stripped on a wiped film still at wall temperatures of 115°C/2 mm Hg in vacuo. The crude oil was wiped film distilled at 165°C/0.4 mm.

1H NMR: 1.21 (t, J=7.14 Hz, 6H), 2.20(s, 6H), 2.21-2.34 (m, 2H), 3.48 (t, J=7.15 Hz, 2H), 4.13 (q, J=7.15 Hz, 4H).

Comparison example 1

This example demonstrates the utility of basic ion exchange resin catalysts. Two identical round bottom flasks equipped with a nitrogen inlet or magnetic stirrer were charged with 46.96 g (0.361 mol) of EAA and 12.96 g (0.159 mol) of 37% aqueous formaldehyde. In one flask, 1.46 g of Amberlite IR 400 (OH) catalyst was added and no catalyst was added to the other flask. The reactions were followed by gas chromatography. The course of the reactions with time was as follows: % EAA remaining

Comparison example 2

In a 500 ml 3-neck flask equipped with a magnetic stirrer, thermometer and nitrogen inlet 210 ml (214.4 g, 1.648 mol) of EAA, 80 ml (83.52 g, 0.787 mol) of benzaldehyde and 2.2 ml of piperidine in 5.5 ml of ethanol were added. The solution was left at room temperature for 4 days and then the solid mass was filtered and recrystallized from petroleum ether/acetone to give 193.85 g (71%) of an adduct which was later shown to be the cyclohexyl derivative 2d (R=C₂H₅, R²=H)

1H-NMR: 0.79 (t, J=7.7 Hz, 3H), 1.05 (t, J=7.7 Hz, 3H) 1.24 (s, 3H), 2.48 (dd, J=13.1, 2 Hz, 1H), 2.71 (d, J=13.9 Hz, 1H), 3.02 (d, J=13.1 Hz, 1H), 3.62-3.74 (m, 2H), 3.76-3.91 (m, 2H), 3.91-4.11 (m, 2H), 7.18-7.24 (m, 5H), 13C-NMR: 13.33 (CH₃), 13.67 (CH₃), 28.44 (CH₃), 45.11 (CH), 52.60 (CH2), 56.90 (CH), 60.96 (CH2), 62.42 (CH2), 73.01 (C), 127.94 (CH), 128.21 (CH), 128.80 (CH), 138.28 (C), 167.94 (C), 174.20 (C), 201.72 (C). IR: 3510, 3090, 2990, 2970, 1739, 1709, 1459, 1375, 1180 cm-1. FDMS: 348.

Comparison example 3

In a 1 L 3-neck flask equipped with magnetic stirrer and nitrogen inlet were added 253.3 g (1.601 mol) of tBAA, 83.52 g (0.79 mol) of benzaldehyde and 2.2 mL of piperidine in 5.5 mL of ethanol. The solutions were stirred for four days with an additional addition of 1 mL of piperidine in 1.5 mL of ethanol each day. The resulting solid was filtered and recrystallized from acetone to give 16.5 g (5%) of cyclohexyl adduct 2b (R=t-butyl, R2=C6H5) and 81.65 g (42%) of benzylidene acetoacetate.

For 2b: ¹H NMR: 1.08 (s, 9H), 1.23 (s, 9H), 1.35 (s, 3H), 2.45 (dd, J=14.3, 2.3 Hz, 1H), 2.67 (d, J 2.67 (d, J=14.4 Hz, 1H), 2.93 (d, J=12.3 Hz, 1H), 3.50 (d, J=12.6 Hz, 1H), 3.89 (app. t, J=12.2 Hz, 2H), 7.21-7.34 (m, 5H). Example 3 - Preparation of 2.4-diacetyl-3-phenyl-di(t-butyl)glutarate (1b)

In a 3 L 3-neck flask equipped with nitrogen inlet, magnetic stirrer and thermometer, 442 g (4.166 mol) of benzaldehyde, 671 g (4.242 mol) of tBAA and 60 mL of ethanol were charged. The solution was cooled in an ice bath and 8.4 mL of piperidine was added. The solution was stirred at 5-25°C for 18 h, after which an additional 4 mL of piperidine was added. After 24 h, a crude solid was filtered off and washed with acetone to yield 570 g (56%) of an approximately 4:1 mixture of E- and Z- t-butyl benzylidene acetoacetate, determined by integration of the methyl peaks of acetoacetyl at 2.34 and 2.42 ppm.

(Michael reaction of benzylidene acetoacetate with t-butyl acetoacetate). In an oven dried 300 mL 3-neck flask equipped with magnetic stirrer, nitrogen inlet, dropping funnel and thermometer was charged 17.8 g (0.1125 mol) of tBAA in 50 mL of diethoxymethane (DEM). The solution was cooled to -14ºC and 1.21 g (=.0108 mol) of potassium tert-butoxide was added. The solution was stirred for 20 minutes and a solution of 25 g (0.01016 mol) of t-butyl benzylidene acetoacetate in 75 mL of DEM was added. After the addition was complete, the Solution was stirred at -7-0°C for 3.5 h and then extracted with saturated NH₄Cl. The organic phase was extracted with methylene chloride and washed with CuSO₄, water and brine. The resulting extract was dried over MgSO₄, concentrated in vacuo and recrystallized from acetone/petroleum ether to give 17.03 g (41%) of 1b, (A=CHPh, R =CH₃, R=t-butyl) mp 133-134°C.

¹H-NMR: 1.11 (s, 18H), 2.19 (s, 6H), 3.81 (d, J=9.8 Hz, 2H), 4.18 (t, J=9.8 Hz , 1H), 7.12-7.31 (m, 5H). 13C NMR: 27.34 (CH3), 29.06 (CH3), 43.10 (CH), 65.74 (CH), 82.08 (C), 127.28 (CH), 127.96 (CH), 129.78 (CH), 138.23 (C), 166.97 (C), 202.79 (C). IR (KBr): 3055, 2985, 2940, 1730, 1700, 1360, 1160 cm¹. HR-FDMS: 404.2201 (calcd for C₂₃H₃₂O₆ : 404.2109).

Example 4 - Preparation of 1,4-bis-2-acetopropanecarboxylic acid benzene di-t-butyl ester

In a 300 mL 3-neck flask equipped with nitrogen inlet, magnetic stirrer and thermometer were charged 20.9 g (0.156 mol) of terephthalaldehyde, 49.73 g (0.314 mol) of tBAA and 110 mL of methanol. Once the solution became homogeneous, 3 mL of a catalyst solution prepared from 2 mL of piperidine, 0.3 mL of acetic acid and 5 mL of methanol was added. After 18 h, the resulting solid was filtered, recrystallized from acetone/methanol and washed with heptane to give 38.9 g (60%) of a product which was a mixture of the EE, EZ and ZZ isomers.

1H-NMR: 1.527, 1.534 (s, 18H), 2.34, 2.41, 2.42 (s, 6H), 7.34-7.58 (m. 6H). IR: 2995, 2975, 1720, 1660, 1620, 1391, 1365, 1245, 1155 cm-1. HR-FDMS 414.2046, (calcd for C24H30O6 :414.2034). Anal. C 69.69%, H 7.62%, (calculated for C₂₄H₃�0O₆ : C 69.55% H 7.48%).

The resulting material was hydrogenated by placing 10.64 g (0.0257 mol) of unsaturated bis-acetoacetate, 100 mL of ethyl acetate, and 0.2 g of 5% Pd on carbon in a Fischer-Porter pressure flask. The flask was purged with nitrogen and then pressurized to 75 psi static pressure using hydrogen gas and held at that pressure for 13 h. The catalyst was removed by filtration and the resulting product was purified by crystallization from acetone/heptane to give 8.96 g (83%) of product, mp 89-90.5°C.

¹H-NMR: 1.39 (s, 18H), 2.17 (s, 6H), 3.06 (m, 4H), 3.65 (t, J=7.7 Hz, 2H), 7.09 (8, 4H). ¹³C-NMR: 27.63 (CH₃), 29.23 (CH₃), 33.27 (CH₂), 62.19 (CH), 82.07 (C), 129.11 (CH), 136.80 (C), 168.55 (C), 203.23 (C). IR (KBr): 2965, 2919, 1731, 1711, 1649, 1631, 1365, 1144 cm-1. MS (EI) 306 (11), 289 (10), 204 (20), 144 (95), 69 (45), 57 (100). HR-CIMS 436.2699 ( calcd for C₂₄H₃₄O₆+NH₄: 436.2699). Anal. C 68.75%, H 8.44% (calculated for C₂₄H₃₄O₆ : 68.88%, H 8.19%).

Examples 5-8 and comparative example 5

Formulations were prepared from compound 1a and acrylic resin A as follows:

SOLVENT = 55;45 EEP/MAK

The formulations were stripped onto phosphated steel at different thicknesses and cured at 180-190ºC. The properties of the resulting formulations are shown in Table 1. The improved MEK abrasion resistance data for formulations 5-8 compared to C-5 indicate that material la cross-links acrylic polymer A.

Example 9 and Comparative Examples 6 and 7

Formulations of compounds 1a, the ethyl analogue of 1a and polyester resin B were prepared as follows:

(Solvent = 80/20 MAK/EEP)

The formulations were stripped and cured at 190-240ºC as previously indicated. The results of the tests (Table 2) show that compound la is effective as a crosslinker of the polyester compared to the control system containing no crosslinker or compared to the material of Example 2.

Examples 10-15 and Comparisons 8-12. Use of a common catalyst in coating formulations

Formulations were prepared as before from compound la and polyester B. The following catalysts were added to the formulations:

(Solvent 80/20 MAK/EEP)

The effect of the additives on MEK resistance at different temperatures is given in Table 3. Examination of the data shows that catalysts used in Examples 10-15 effectively lower the cure temperature, whereas the materials of Comparative Examples 8-10 have either no effect or a negative effect on the cure behavior of the compounds.

Example 6 and Comparative Example 13

A formulation of plastic B and crosslinker 3a was prepared as follows:

The formulations were evaluated as follows and the results of these evaluations are summarized in Table 4. The MEK resistance properties and impact strengths of the resulting coatings demonstrate that material 3a is also an effective crosslinker.

Examples 17-19 - Use of di-t-butyl-3,5-diacetyl-4-phenylglutarate as a crosslinker in polyesters

The following formulations were produced:

The formulations were heated in test tubes at 180-220ºC. Insoluble gels were obtained, indicating the formation of cross-linked polymers.

Example 20 and Comparative Example 14

This example demonstrates the improved resistance to atmospheric humidity obtained with coating formulations when using compound 1a.

The pigmented formulations were prepared as follows:

The panels were coated and cured at 230ºC as indicated above. The formulations of Example 20 showed no blistering after > 1000 h exposure in Cleveland Humidity conditions, whereas formulation C-14 showed significant blistering after 727 h.

Example 21

Formulations of compound 1b and plastic A were prepared as follows: Table 1

(a) Temperature (ºC) and time (min) respectively.

(b) Impact strength for the front and back in foot-lbs each. Table 2

(a) Temperature (ºC) and time (min) respectively.

(b) Impact strength for the front and back in foot-lbs each. Table 3

(a) Temperature (ºC) and time (min) respectively.

(b) Impact strength for the front and back in foot-lbs each. Table 4

(a) Temperature (ºC) and time (min) respectively.

(b) Impact strength for the front and back in foot-lbs each.

* Thickness in mm; conversion factor f = 25.4; for example 0.45 mils corresponds to 11.43 mm

** Impact strength in J; conversion factor f = 1.356; For example, 160 ft-lb corresponds to 216.96 joules.

Claims (17)

1. Compound according to formula (1) wherein R is a C₄-C₁₀-tertiary alkyl radical, R¹ is C₁-C₆-alkyl or aryl, and A is a group of the formulas wherein R² is phenyl or A is a C₁-C₁₀-hydrocarbon radical, excluding compounds wherein both R's are tertiary butyl, both R¹'s are methyl and A is a methylene, ethylene or group is. 2. A compound according to claim 1, wherein R is t-butyl. 3. A compound according to claim 1, wherein A is a group of the formula with R² is phenyl. 4. A compound according to claim 1, wherein A 5. A compound according to claim 4 wherein R is t-butyl. 6. A compound according to claim 1 or 3, wherein R¹ is methyl or phenyl. 7. A compound according to claim 1, wherein A is -CH₂-. 8. Process for preparing a compound of formula wherein A is a group of the formula -CH₂-, R is C₄-C₁₀-tertiary alkyl and R¹ is C₁-C₆ alkyl or aryl, comprising contacting a mixture comprising a compound of the formula and aqueous formaldehyde with a basic ion exchange resin. 9. The process of claim 8 wherein R is t-butyl, R³ is methyl or R¹ is phenyl. 10. A curable gloss coating composition comprising (a) 95 to 55% by weight, based on the total weight of (a) and (b), of one or more curable polymers, (b) 5 to 45% by weight, based on the total weight of (a) and (b), of a compound of formula (1) wherein R is a C₁-C₆ alkyl radical, R¹ is C₁-C₆ alkyl or aryl and A is a group with the formulas wherein R² is phenyl or A is a C₁-C₁₀-hydrocarbon radical, and (c) 0 to 50% by weight, based on the total weight of (a) and (b), of a solvent. 11. A curable gloss coating composition according to claim 10, wherein A is a group of the formula 12. A curable gloss coating composition according to claim 10, wherein A is a group of the formula wherein R² is phenyl. 13. A curable gloss coating composition according to claim 10, wherein A is a C₁-C₁₀ alkylene group and R is methyl or phenyl and R is t-butyl. 14. A curable gloss coating composition according to any one of claims 10 to 13, comprising (a) 85 to 60% by weight, based on the total weight of (a) and (b), of one or more curable polymers, (b) 15 to 40% by weight, based on the total weight of (a) and (b), of a compound according to formula (1) and (c) 0 to 35% by weight, based on the total weight of (a) and (b), of a solvent. 15. Curable gloss coating composition according to one of claims 10 to 14, further comprising (d) 1 to 70% by weight, based on the total weight of (a) and (b), of one or more pigments. 16. A curable gloss coating composition according to any one of claims 10 to 15, further comprising one or more leveling agents, flow agents or flow control agents, sanding varnish agents, pigment wetting and dispersing agents and surface-active agents, ultraviolet absorbers, ultraviolet light stabilizers, coloring dyes, defoamers and antifoaming agents, anti-settlement and anti-sagging agents and body-forming agents, anti-skinning agents, anti-overflow and anti-leaking agents, fungicides and anti-mold agents, corrosion inhibitors, thickeners or coalescing agents. 17. A coated, shaped or designed article obtained after application to the article and subsequent curing with a composition according to claims 10 to 16.